Draw the Lewis structure of SO3. The formal charge of Sis [1] +2 [2] +1 137 [5] -2
The Correct Answer and Explanation is:
Answer:
The formal charge of sulfur (S) in SO₃ is [2] +1.
Explanation:
- Lewis Structure of SO₃:
- Sulfur Trioxide (SO₃) is a molecule where sulfur is bonded to three oxygen atoms. It has a trigonal planar geometry.
- Sulfur has 6 valence electrons, and each oxygen atom also has 6 valence electrons. Hence, the total valence electrons for the molecule are: 6+(6×3)=24 electrons.6 + (6 \times 3) = 24 \text{ electrons.}6+(6×3)=24 electrons.
- The Lewis structure consists of sulfur (S) at the center with three double bonds to each oxygen atom. Each oxygen atom also has two lone pairs of electrons to fulfill the octet rule. This structure uses 24 electrons: 6 for the bonds (3 double bonds × 2 electrons) and 18 for the lone pairs.
- Formal Charge Calculation:
- The formula for formal charge is: Formal charge=(Valence electrons)−(Non-bonding electrons)−12(Bonding electrons).\text{Formal charge} = (\text{Valence electrons}) – (\text{Non-bonding electrons}) – \frac{1}{2}(\text{Bonding electrons}).Formal charge=(Valence electrons)−(Non-bonding electrons)−21(Bonding electrons).
- For sulfur:
- Valence electrons = 6.
- Non-bonding electrons = 0 (no lone pairs on sulfur in this structure).
- Bonding electrons = 12 (6 bonds, each with 2 electrons).
- Formal charge: 6−0−122=+1.6 – 0 – \frac{12}{2} = +1.6−0−212=+1.
- For each oxygen:
- Valence electrons = 6.
- Non-bonding electrons = 4 (2 lone pairs).
- Bonding electrons = 4 (2 double bonds).
- Formal charge: 6−4−42=0.6 – 4 – \frac{4}{2} = 0.6−4−24=0.
- Significance of Formal Charge:
- The sulfur atom has a formal charge of +1, and each oxygen atom has a formal charge of 0. This makes the structure neutral overall.
- Resonance:
- SO₃ has resonance structures, meaning the double bonds can shift between the oxygen atoms. However, the formal charge on sulfur remains +1 in all resonance forms.
This structure balances formal charges while following the octet rule, where possible.